Warm rolling facility for steel strip coils

ABSTRACT

The present invention relates to a warm rolling facility suited to rolling of brittle strip coils such as high Si steels. The facility is provided with a rolling machine, tension reels disposed respectively at an inlet side and an outlet side of the rolling machine, deflector rolls between each of the tension reels and the rolling machine. The tension reels are positioned in warming furnaces having heating means, and the rolls and the deflector rolls are provided with means for heating the rolls. Further, the rolling machine is provided at its inlet and outlet with heating apparatuses for heating the strip.

This is a continuation of application Ser. No. 584,364, filed Sep. 17,1990, now abandoned, which is a continuation of application Ser. No.294,610 filed Dec. 15, 1988, now abandoned.

TECHNICAL FIELD

The present invention relates to a warm rolling facility suitable tothin plates, especially with less workability.

BACKGROUND OF THE INVENTION

Recently, from standpoint of saving natural sources and energy, smallsizings and high efficiency of electromagnetic or electronic parts havebeen demanded, and soft magnetic property, especially Si steel sheetshaving excellent iron loss have been also required. It is known thatsoft magnetic properties of Si steel sheets are improved with increasingof addition of Si and exhibit the maximum permeability at about 6.5 wt%, and since natural electric resistance is high, the iron loss is madesmall. In this kind of steel sheets, if the Si content is less than 4.0wt %, workability is abruptly worsened, and therefore it has beenimpossible to produce high Si steel sheets in industrial scales by therolling process, but it has been found that the warm rolling could beperformed on the thin steel sheets through studies.

However, ordinarily used rolling facilities could not secure bendingdeformation of the coil or temperatures of the materials, and aredifficult to roll the high Si steel sheets. For example, Japanese PatentApplication Laid-Open No.135,407/86 proposed a facility protecting froman uncoiling reel to first rolling stands with a warming wall, but thisfacility could not prevent cracks by bending at the deflector rolls orby rolling.

This invention has been developed in view of problems involved with theprior art, and is to provide a warm rolling facility which may carry outthe rolling efficiently without causing cracks in thin steel sheets withless workability.

DISCLOSURE OF THE INVENTION

For accomplishing this object of the invention, the strip is subjectedto reverse rollings between tension reels, while it is always maintainedat determined temperatures, whereby the facility could prevent cracks orbreakages by bending and working. The facility is constructed with arolling machine, tension reels disposed respectively at an inlet sideand an outlet side of the rolling machine, deflector rolls between eachof the tension reels and the rolling machine. The tension reel ispositioned in a warming furnace having a heating means, and the rollsand the deflector rolls are provided with heating means for the rolls.Further, the rolling machine is provided at the inlet and the outletwith heating apparatuses for the strip.

In this rolling facility, the strip is undertaken with the reverserollings, and in a case of high Si steel sheet, the hot rolled coil of 2mm thickness is ordinarily rolled to thickness of about 0.5 mm. Therolls are preheated about 200° C. (surface temperature) by heatingmeans, and the defector rolls are also always preheated at about 200° C.(surface temperature) by heating means. The strip coil is kept at thetemperatures between about 300° and 600° C. in the warming furnace. Thestrip which is uncoiled from one of the tension reels and sent from thewarming furnace, passes the deflector rolls and is rolled. Since thedeflector rolls are heated, the strip passing thereon is avoided fromdecreasing of temperature, so that the strip is checked from bending orbreakage at the deflector rolls. The strip passing the deflector rollsis heated for securing the temperature of the strip to be rolled andgoes into the rolling machine. Since the rolls are preheated, the stripis controlled to the minimum from escaping of the temperature at therolls. The strip from the rolls is heated by the heating means disposedat the outlet of the rolls, and passes the heated deflector rolls and iscoiled by another tension reel within the warming furnace. The strip isheated and maintained at the temperatures about from 200° to 600° C.,and thus the rolling is repeated on the strip to reduce it to a thinsheet.

The strip is always maintained above the determined temperature (forexample, more than 200° C.) during the reverse rolling, and the rollingis carried out as exactly avoiding crackings, breakages by the bendingor the working at the tension reels, the deflector rolls and the rollingparts.

In the rolling of the high Si steel sheet, the strip is kept heatedbetween each passes of the reverse rolls in warming furnace, so thatrecovery treatment is made between the passes and the maximumpermeability is improved. That is, strain caused in the steel structureduring the rolling is released moderately by the heating treatment atlow temperatures in that the strip is kept heated within the warmingfurnace, and the coherent structure of the final product is changed byrepeating causing of the strains in the steel structure and releasing ofthe strains, and as a result, the magnetic property is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing one example of the invention;

FIG. 2 is a diagram showing air cooling of temperature in accordancewith thickness of a strip; and

FIG. 3 is a diagram showing decreasing of temperature of the strip bycontacting the rolls during operation, in relation with the temperatureof the surfaces of the rolls and the temperature after rolling thestrip.

MOST PREFERRED EMBODIMENT FOR PRACTICING THE INVENTION

The invention will be explained with reference to embodiment shown inthe attached drawings.

FIG. 1 shows one embodiment of the invention where a rolling facility isprovided with a rolling machine 1, tension reels 2a,2b disposed at aninlet and an outlet thereof, and deflector rolls 3 positioned betweeneach of the tension reels and the rolling machine.

The tension reels 2a,2b are positioned in warming furnaces 4a,4b havingheating means. Each of the warming furnaces 4 is constructed as a gasfurnace having a heating burner 5. As the heating means, appropriateones may be used.

Heating apparatuses 6a,6b are provided at the inlet and the outlet ofthe rolling machine 1 for heating a running strip. As the heatingapparatus, a heating furnace may be used which has a gas furnace (e.g.,C gas furnace), an electric radiant heater or radiant tubes.

The deflector rolls 3 are positioned by two at the inlet and the outletof the rolling machine. Each of the deflector rolls 3 is provided with aheating means, and in the present embodiment, the deflector roll isallowed to pass an oil therewithin at high temperature. As other heatingmeans, such may be employed which is disposed with a burner directlyheating the surface of the roll, or housed with an electric heaterwithin the roll. Number of the deflector rolls gives influences tobending degree of the strip, and more than one are disposed inaccordance with diameters of rolls or positioning conditions of therolls.

The rolls 7 are provided with heating apparatuses for preheating therolls, and in this embodiment, heating burners 9 stand against thevertical rolls 7. It is possible to compose a structure, as the heatingmeans therefor, nozzles for supplying the oil at high temperature standagainst back-up rolls 8 for preheating rolls 7 via the back-up rolls 8.

The numeral 10 designates a thickness measuring instrument, 11designates thermometers, and 12 a lubricating grease supply.

The rolling machine 1 of this embodiment has four rolls, and others maybe used as five, six rolls or planetary rolling machine, and a reverserolling machine is not only one stand bu also plural stands. In theplural stands, the heating apparatuses are positioned at the inlet andthe outlet of each of the rolling machines, thereby to carry out therolling operation efficiently.

According to the above mentioned rolling facility, the strip coil (A)within the both warming furnaces 4a,4b is normally maintained at thetemperatures of 200° to 600° C., and each of the deflector rolls 3 isalways heated to keep the temperatures of around 200° C. on the surface.The rolls 7 is preheated or heated to be around 200° C. on the surface.

The strip (S) at about 200° to 600° C. uncoiled from one of the tensionreels 2 is bent by the deflector rolls 3 and sent to the rolls 7. Sincethe deflector rolls 3 are heated at about 200° C., the strip (S) runs askept at least this temperature without causing breakage. The strip (S)is introduced instantly into the heating apparatus 6a and heated to therolling temperature, and reduced in thickness by the rolling machine 1.Since the rolls are heated or preheated, the strip is also hereprevented from escaping of the temperature. The rolls are notnecessarily heated always, and for example, it is possible to preheatthe strip fully at a beginning step so as to avoid the strip fromdecreasing of the temperature, and maintain the rolls at the determinedtemperature by heat conductivity from the strip.

The rolled strip (S) is introduced instantly into the heating apparatus6b of the outlet and heated, and passes the deflector rolls 3 heated onthe surface at about 200° C. as stated above, and coiled to the tensionreel 2b in the warming furnace 4b. The strip (S) is rolled reverselybetween the tension reels 2a,2b to a determined thickness.

FIG. 2 shows the decreasing of the temperature by the air cooling(decreasing from the temperature of 400° C. of the strip in theatmosphere of 25° C.) in response to the strip thickness. Thetemperature largely decreases in the thin strip. If the strip wererolled without the heating means between the tension reels, the warmingcondition could not be kept. FIG. 3 is a diagram showing decreasing oftemperature of the strip by contacting the rolls during the rollingoperation, in relation with the temperature of the surfaces of the rollsand the temperature after rolling the strip. The strip is prevented fromdecreasing of the temperature effectively by maintaining the rollsurface at the determined temperature.

When the high Si steel strip is subjected to the reverse rolling and ifthe strip (S) is maintained for a determined time (normally 1 to 10min.) in the warming furnaces 4a,4b between each passes, the recoverytreatment between the passes is carried out (the heating treatment atlow temperatures of 300° to 600° C). Strain caused in the steelstructure during the rolling by the recovery treatment between thepasses is released moderately, and the coherent structure of the finalproduct is improved in the magnetic property by repeating causing of thestrains in the steel structure and releasing of the strains.

Each of the rolls 7 is supplied with a heat resistant lubricating grease(for example, the grease having an ignition point of more than 300° C.)from a lubricating grease supply 12.

When a supply device of an oil at high temperature is provided as aheating means of the rolls, the back-up rolls 8 are applied with the oilof more than 200° C. for preheating the rolls 7 via preheating of theback-up rolls.

According to the present invention, since the reverse rolling can beundertaken while the strip is always maintained above 200° C. at whichthe bending or rolling reduction is loaded to the strip, the rolling canbe performed on even such steel strips with less workability containingmore than 4.0 wt % Si, without causing cracks or breakage in the strip.

In the case of the high Si steel, the strip is subjected to the recoverytreatment between the passes by keeping warmed between each passes ofthe reverse rolling, thereby to improve the magnetic property of thefinal product.

INDUSTRIAL APPLICABILITY

The present rolling facility may be applied to rolling of thin plateswith less workability such as high Si steels.

What is claimed is:
 1. A warm rolling facility for silicon steel stripcoils, comprising in combination a rolling machine 1 having an inlet andan outlet and rolls 7 and a heating burner 9 adapted to pre-heat saidrolls 7, at least two warming furnaces 4a,4b, a tension reel 2a,2bsupported within each warming furnace and disposed at said inlet andoutlet, respectively, a plurality of individual deflector rolls 3provided with deflector roll heating means and disposed outside of saidwarming furnaces and between the tension reels and the rolling machine,heating means 6a,6b disposed at said inlet and outlet, respectively, forheating a passing steel strip, wherein said heating means 6a,6b and saiddeflector roll heating means comprise a plurality of componentsgenerating heat, which components are arranged in closely spaced seriesthroughout the passage traversed by the steel strip between said tensionreels for the purpose of maintaining said steel strip at a predeterminedtemperature throughout said passage.
 2. The facility as claimed in claim1, wherein the roll heating burner 9 directly heat the rolls
 7. 3. Thefacility as claimed in claim 1, wherein the roll heating burner 9indirectly heat the rolls 7 via back-up rolls
 8. 4. The facility asclaimed in claim 1, 2, or 3 provided with the rolling machines having aplurality of stands.
 5. The facility as claimed in claim 1, 2, or 3wherein the heating means for the deflector rolls are constructed forflowing heating medium within the rolls.
 6. The facility as claimed inclaim 1, 2, or 3 wherein the heating means for the deflector rolls heatthe rolls outside thereof.
 7. The facility as claimed in claim 1, 2, or3 provided with lubricating grease supply to vicinity of the rolls.
 8. Amethod of rolling a travelling silicon steel strip by carrying outreverse rollings between first and second tension reels disposed infirst and second warming furnaces, respectively, while maintaining saidstrip at a predetermined temperature by continuously performing thesteps comprising:uncoiling said strip from said first tension reel assaid strip leaves said first warming furnace while keeping said stripheated in the first warming furnace; deflecting the path of said stripwith a first deflector roll maintained at a predetermined temperature;further deflecting the path of said strip with a second deflector rollmaintained at a predetermined temperature; heating said strip prior tosaid strip entering a rolling machine; rolling said strip by means ofpreheated rolls in said rolling machine; heating said strip after saidstrip exits said rolling machine; deflecting the path of said strip witha third deflector roll maintained at a predetermined temperature;further deflecting the path of said strip with a fourth deflector rollmaintained at a predetermined temperature; and coiling said strip onsaid second tension reel in said second warming furnace and keeping saidstrip heated in said second warming furnace.
 9. The method of claim 8,wherein said predetermined temperature of the steel strip is not lowerthan 200° C.
 10. The method of claim 8 or 9, comprising reverse rollingsaid steel strip between the first and second tension reels and keepingsaid strip heated in the warming furnace between each pass of thereverse rolls, whereby recovery treatment is made between the passes.